Fluid-blast electric circuit breaker



Dec. 5, 1950 D..F. AMER 2,532,529

FLUID-BLAST ELECTRIC CIRCUIT-BREAKER Filed Jan. 20, 1948 5 Sheets-Sheet l T/ f l V Inventor CUaJa-.v M, am Atlorney Dec. 5, 1950 D. F. AMER FLUID-BLAST ELECTRIC CIRCUIT-BREAKER 5 Sheets-Sheet 2 Filed Jan. 20, 1948 Inventor aha-k. Attorney Dec. 5, 1950 D. F. AMER 2,532,529

FLUID-BLAST ELECTRIC CIRCUIT-BREAKER Filed Jan. 20, 1948 5 Sheets-Sheet 3 M l D4 D3 l B3 'il .wv

Inventur D. a1. lw/ B WLUALM llor/xey Uma-MJ, M/

Dec. 5, 1950 D. F. AMER FLU1DBLAST ELECTRIC CIRCUIT-BREAKER Filed Jan. 20, 1948 5 Sheets-Sheet 4 Dec. 5, 1950 D, F. AMER 2,532,529

FLUID-BLAST ELECTRIC CIRCUITBREAKER Filed Jan. 20, 1948 5 Sheets-Sheet 5 y' i l 'Ql- Q le:`-`

2 .ll-la www Allorney Patented Dec. 5, 1950 FLUID-BLAST ELECTRIC CIRCUIT BREAKER Donald Foster Amer, Newcastle-on-Tyne, England, assignor to A. Reyrolle & Company Limited, Hebburn-on-Tyne, England, a British company Application January zo, 194s, serial No. 3,243

In Great Britain February 3, 1947 'Ilhis invention relates to fluideblast electric circuit-breakers kof thekind in which relative movement of them-operating contacts is effected by fluid pressure within an arcing chamber or contact enclosure,

In an electric circuit-breaker according to the invention one or each of the vco-operating contacts is located by a' flexible or resilient device (such for example vas a diaphragm, bush or bellows), situated within the arcing chamber or enclosure so thatfrictional sliding or guide surfaces for the contact or contacts can be obviated.

The contacts may separate adjacent to at least one nozzle or vent 'through which the arc is driven by the blast ofv arcexting'uishing huid from the enclosure. For example, one or each of the cooperating `contacts may itself constitute a nozzle or vent. In one arrangement, the co-o-perating contacts carry the relatively movable parts of a duid-tight valve which controls the flow of arcquenching fluid from the enclosure to an exhaust conduit or conduits formed, for example, in one or each of the co-operating contacts.

In the accompanying drawings,

Figures 1 to 3 are diagrammatic representations, in vertical section, of three arrangements of single-break circuit-breaker embodying the invention,

Figure 4 shows, also in vertical section, one unit of a high voltage multi-break circuit-breaker having a plurality of circuit-breaker units arranged in .a series stack.

Figure 5 is a diagrammatic representation of such multi-break circuit-breaker with contact control by pressure release( Figure 6 similarly illustrates a modification of Figure 5 in which each pair of co-operating oontacts together form a fluid-tight seal, and

Figure 7 is a modication of Figure 6, the contact lcontrol being effected by control of the supply of pressure nuid. v

In the lconstruction shown in Figure 1, the sinn gle-break circuit-breaker comprises a fixed arcing Contact A disposed coaxially within lan externally shedded cylindrical insulating enclosure B, the lower end of the fixed contact A. being electrically connected to a spider A1 carried by the enclosure B and constituting one pole X of the circuitbreaker. Mounted on the upper end of the enclosure B is a metallic nozzle member or cap C which incorporates a nozzle C1 Whose axis is substantially in alignment with the axis of the xed contact A, the nozzle C1 haring towards an auxiliary electrode D electrically connected to the nozzle member C. Disposed laterally with respect to the fixed contact A and adjacent to the 14 Claims.v (Cl. v20D- 148) nozzle C1 is a moving Contact E carried by a ilexihle diaphragm, disc or bellows (dagrammatically indicated at E1) of conducting material arranged When the circuit-breaker is to be opened, an

inlet `control valve F1 at the base of the enclosure B is opened so that pressure uid, for example air under pressure, is supplied from a receiver or reservoir F to the interior of the enclosure B. The uid pressure within the enclosure B now acts on the diaphragm E1 and thus causes the moving contact E to be retracted from the xed Contact A. The arc initiated between the fixed and moving contacts A, E is now transferred, by the blast of deionising fluid, from the moving contact E to the nozzle member C and, through the nozzle C1, to the auxiliary arcing contact D, the arc being thus extinguished. As soon as the inlet control valve F1 is closed, the moving contact E will be automatically restored to its closed position. In the latter respect the valve F1 and a series break isolating switch indicated at Z are sequentially controlled so that when the arc has been extinguished the isolating switch Z is opened before the valve F1 is reclosed, re-establishment of the circuit being subsequently effected by closing the isolating switch Z.

It will be apparent that, since the moving contact Eis located solely by the resilient diaphragm E1, frictional sliding surfaces or guide surfaces for the moving contact E are Wholly obviated. Though, with this construction, it is preferred to empl-cya locating device E1 of metal since this provides also for positive electrical connection between the moving contact E and the nozzle member'C and, moreover, will satisfactorily withstand the effects of arcing, it may be desirable in some instances to employ resilient or flexible locating' device of insulating material, such for example as rubber. To this end, the moving contact may be located by a rubber bush, disc or sleeve, the moving contact being electrically connected to the nozzle member C through one or more flexible leads. Whether the locating device El is of conducting material or of insulating material, however, it will be understood that the flow of deionising iluid through the enclosure B to the nozzle C1 will tend to sweep the products of arcing away from the iiexible locating device El thus tending to protect this device against the elects of arcing.

In the construction shown in Figure 2 the insulating enclosure G is furnished with a contact ring or spider G1 which constitutes one pole X of the circuit-breaker, the spider G1 carrying a iixed contact G2 disposed coaxially within the enclosure G, Arranged in alignment with the fixed contactv G2 and secured to ia second lixed spider H1 carried by the enclosure G (this spider H1 constituting the second pole Y of the circuitbreaker) is a hollow or tubular carrier I-I for a moving contact ring H2 which is located on the tubular carrier by a flexible disc H3 of conducting material, or oi insulating material such, for example, as rubber' bonded to the contact VH2 and carrier H. A biasing spring H4 disposed Within the hollow contact carrier H urges the moving contact H2 into abutment with the .fixed contact G2. Il the flexible locating device `is of conducting material this device itself forms rthe necessary electrical connection with the tubular 0r .hollow contact I.carrier H and ,therefore with the -second pole Y of the .circuit-breaker, `but if the -flexible locating device H3 is c-f insulating material, the necessary electrical contact may be provided by one ior more flexible leads H5 arranged within the hollowcontact .carrier H.

kThe spider 4H1 is provided .with an exhaust passage H6 so that,-assuming .the :contacts G2H2 t obe .in mutual abutment and .it .is desired to open the circuit-breaker, .the 'inlet control valve E1 is opened so that duid is delivered from .the reservoir F to the enclosure G. The pressure .of the `fluid in the enclosure G then acts on the flexible or resilient locating -device `I-I3 .so as to separate the contacts G2H2 against the action of thebiasing spring :l-I4. A blasto fluidthen ows from'the -enclosure G-between the contacts G2H2 and thence out through the exhaust passage H6 to vthe atmosphere. The moving vcontact H2-may bein the forni of a nozzle so lthat the arc initiatedbetween the contacts `G2H2 when they separate .is transferred through Vthe nozzle and is thus extinguished. Y

It will be appreciated that leither the xed contact or the moving contact, or both, may be v'hollow and nozzle-like, though it will usually be preferred to make the ixed 4contact in the form of .a nozzle, for example'as will be described below with ureference toFigures 3 and 4. In some instances it may be preferredto provide two contact tips or plates each carried by a resilient or ilexible locating disc, diaphragm, bush or bellows, either or each of the two carriers for the two Acontacts (both of which are thus movable) being hollow and furnished with exhaust passages.

According to the construction shown in Figure 3, instead of the separation of the contacts being controlled by an inlet control valve, that is to say by a valve controlling the delivery of pressure fluid to the enclosure, the separation of the contacts is effected by an outlet control valve which relieves or releases the uid pressure acting on the movable contact externally to the enclosure. In this construction each of the two spiders J, K is hollow, so as to provide for the exhaust or release of pressure fluid therefrom. To this end, one spider J carries a hollow fixed contact J1 having its open end J2 within the enclosure J3 formed as a nozzle. The second spider K carries a hollow fixed tube K1 in axial alignment with the hollow contact J1. Co-operating with the nozzle-like Vend J2 of the xed hollow contact J1 is a movable contact K2 locat-ed on. the carrier K1 by a flexible or resilient locating device K3 in the form of a disc, bush or bellows. As with the constructions above described, the movable contact K2 may either be electrically connected to its hollow carrier K1 by the locating device K3 if this is of conducting material or, if the device :Kiiseo'f insulating material (for example a rubber disc), the movable contact K2 may be connected to the spider K through one or more flexible leads K4 disposed within the ltubular :carrier K1 which also houses a biasing springK5 for restoring the moving con- .tact`K2 to its closed position after opening of the contacts.

The hollow carrier K1 has a relief passage K6 communicating with a relief conduit provided with an Voutlet control valve K'I so that, when the fluid pressure is maintained within the enclosure U3 from a supply conduit J4, opening of the outlet control valve K7 will result in the predominating flu-id pressure within the enclosure 'J3 acting .to separate .the .contacts `J2K2.. As the two contacts separate, `a .blast .of .deionising .fluid ilows over .the separating `contacts and thence through the carrier J1 to the atmosphere. The arc is thus blown through Vthe nozzle-'like end J2 of the lixed contact, the .products of arcing being discharged vthrough the .exhaust passage J5. The carrier K1 is in open .communication with the enclosure YJ3 through a bleed passage J 6 so that, after opening the circuit-breaker `and reclosing the outlet 4)control valve K7, pressure fluid will leak through the bleed passage `J6 until the .pressure in the .hollow carrier K1 is again euual to vthatv within the enclosure J3 -in readiness -for the next opening operation;

Vr-lhe invent-ion is particularly, though not ex clusively, applicable -to circuit-breakers of the multiebreak type comprising a plurality of Acontact Aunits arranged in an aligned series or stack. In one such construction, as .shown in Figure 4, each contact unit is larranged -in a cylindrical sbeded enclosure B1 furnished with an external harige-like metal annulus B2 .having .an exhaust port or ports B4 through which the arc `@clenching fluid is discharged through an exhaust valve B3 of the flap type. rIhe lannulus B2, which constitutes one terminal of the unit, forms par-t foi a conducting Vspider A3 having a cylindrical lcarrier A2 disposed coaxial'ly within the enclosure B1. rihe upper or open end A4 yof the hollow carrier A2 is formed into a .nozzle-like contact, and an auxiliary arcing electrode D1, which is also hollow, is arranged within the xed contact A2 in alignment with. but spaced below, the contact A4. vA disc-like moving contact D2 is secured 'to the lower end of the hollow carrier A2 by means of a ilexihle locating device D3, such for example as a disc of copper, the moving contact D2 having an axial anchorage stud D4 connected through adjusting nuts AD5 and 'an anchorage chain Ds to the interior of the auxiliary arcing electrode D1. A biasing spring D7 bears at its, lower end against the assembly vof the movn ing contact D2 and at its upper end against an in# ternal flange or shoulder D8 of the auxiliary arcing electrode D1, the travel of the moving contact D2 under the action of the biasing spring Drl being thus Vlimited by the eiective length of the anchorage chain D6 as determined by the adjusting nuts D5.

Thus, the iixed contact A2, A4, auxiliary electrode D1 therein, the movable contact D2 immediately below the fixed contact, and the terminal annulus B2 with whose exhaust port or ports B4 the-interior of the carrier A2 isl in open communication, together constitute one contact unit associated with one enclosure B1, and it is to be understood that this unit, all parts of which are at the same potential, does not' in itself constitute a break. When, however, a plurality of the units are secured together in a series stack by means of clamps B5 associated with the terminal annuli B2 at the lower ends of the units and terminal annuli B6 at their upper ends, the moving contact D2 of any one unit will bear against the rim of the nozzle A4 at the upper'or open end of the next lower unit, the ycurrent owing from one pole of the circuit-breaker constitutedxby the lowermost terminal annulus B2, through the iixed and moving contacts A4D2 of the stack in series and finally to the other pole of the circuit-breaker constituted bythe uppermost annulus B5.

4The interiors ci the severalenclosures B1 are all in open communication with each other through openings in the spiders A3 so that when it is desired to open the circuit-breaker anl inlet control valve F1 (as described with reference to Figure l) is opened so that iiuid under pressure is delivered from a reservoir to the enclosures B1. The fluid pressure within these enclosures now acts on the several movingr contacts D2 and raises them from the associated iixed contacts or nozzles A4. As each pair of co-operating contacts D2, A4 separates, a blast of deionising iiuid flows radially inwards between these contacts and through the hollow fixed contacts A4A2 to the atmosphere through the exhaust ports B4. The blast of deionizing uid transfers the ,arcs ,initibetween the separating contacts through the nozzles A4 to the associated auxiliary arcing electrodes D1, the uid blasts iinally extinguishing the arcs whereupon the closing of the inlet control valve F1 and resulting fall in pressure within the several enclosures B1 permits the moving contacts D2 to be restored into abutment with their associated lixed contacts A4 by the'springs DT. AAs in the constructions above described, the resilient locating device D3 for the moving contact D2 of each unit obviates the necessity for any frictional slidingr or guide surfaces for any of the contacts. It will, however, be understood that though a metal disc or diaphragm has been more specifically described, the iiexible or resilient locating device D3 may be constituted by a diaphragm of insulating material such, for example,

as rubber, or by a rubber sleeve or. bush. or by a bellows. When the locating device D3 is of insulating material the electrical continuity between the contact A2 and the moving contact D2 of each contact unit may be provided by one or more flexible leads D8 arranged within the hollow auxiliary arcing electrode D1. v

. The shedded insulating enclosure B1 for eac contact unit is so formed that the external surface resistance path of each shed B exceeds that of the cylindrical parts B8 of the enclosure so that the greater part of the said surface resistance is at right angles to the longitudinal axis of the' enclosure, or stack of alignedenclosures. A resistance or capacitance may `be connected across each break of the multi-break series stack so that the voltage is substantially uniformly distributed over all the breaks, V'I'he resistances are constituted by an external semi-conducting glass on the shedded enclosures B1 so that the resistance between any two corresponding points on any two sheds B7 respectively is the same as or proportional to that between such corresponding points o n any other two sheds B7.

Tharesistance' glaze, combined with mainly radial insulation, permits the use of metal parts of adequate dimensions without increasing the length of the stack of contact units. the radial formation of the insulator sheds BI providing adequate surface length between the metal iittings (i. e. the terminal annuli B2, B6) for the voltage distribution to be controlled by the resistance glaze. As a result, the edges of the sheds B'I are at a potential approximately midway between those of the associated metal ttings and the overall length necessary is no more than the sum of the overall lengths of the units since the said overall length of the stack is determined by the lll) distance between the ends of the sheds BFI and not by the distance between the metal ttings B2, B6.

In the construction shown in Figure 5, instead of the` separation of the contacts being effected by supplying uid pressure, such for example as air, through an inlet control valve to the vstacked enclosures, the said separation is effected by means of an outlet control valve F3 which relieves or releases the iiuid pressure on each movable contact L externally to the enclosure M. In this construction, each contact unit comprises a hollow fixed contact M1 electrically connected to the moving contact L below it as described with reference to Figure 4 above. An associated hollow or tubular auxiliary arcing electrode M2 is arranged within the. nozzle-like fixed contact M1, the exhaust passage M2 for each nxed contact M1 being formed in the associated supporting spider M4 and terminal annulus. Each tubular auxiliaryarcing electrode M2 containing the necessary biasing spring or springs M5 for the moving contact L andthe lead Ni6 provided when the flexible locating device L1 is of insulating material, is in open communication with a common relief conduit F4 controlled by the said outlet control valve F3.

With this arrangement, the interiors of the aligned enclosures M, which are again all in open communication witheach other through open- Y ings in the spiders M4, are maintained filled with the pressure iiuid from the reservoir F, each tubular auxiliary arcing electrode M2 being in open communication with the interior of the enclosure through a bleed passage such as the passage J6 shown in Figure 3. Thus, when the contacts L, Ml are in the abutting position. shown in Figure v5, the pressure within the relief conduit F4 is equal-to that within the stacked enclosures M. When, however, it is desired to open the circuit-breaker, the outlet control valve F3 is opened and the iluid pressure within the tubular auxiliary electrodes M2 thus relieved. The predominating uid pressure within the enclosures M is now eiective to separate the contacts L, M1. so that the blasts of deionising uid ilow between the separating contacts and out through the exhaust conduits M3.

As indicated above, since the main contacts of the circuit-breaker vautomatically reclose after arc extinction, means Will be provided for isolating the circuit after the arc extinction is cornplete. To this end, the circuit-breakers of Figures 2 to 5 will be provided with series-break isolating switches such as theswitch Z described with reference to Figure l,the isolating switch and uid control valve being actuated se uen.- v tially, for example as shown diagrammatically in Figure 5 in which the valve F3 is actuated by a rod P6 which acts through a lost-motion coupling Plon the isolator Z.r

7 Thel relatively movable contactsnray vhave associal-.ed seatings which` rio-operatel` in a ui'ds" tight man-ner so: as 'to constitute the rela-tively movable' parts oi a iiuidecontrol. valve.. For examlple',.as shown in Figuret 6 which is a mo'diii'cai tioiiof the arrangement shown in Figure 5, the sta-ck of enclosures M is again mounted upon a reservoir O Awith thecontrol valve F3 and reliei passage Each moving contact L is carried by u resilient, e. g. rubber, 'diaphragm L1, but in addition to the contacts L making butt Contact with the fixed nozzle-alike' contacts M1, each diaphragm vL1- coecperates Aas a resilient 'huidaigiht seating' with a Ysea-ting flange' Mion the asso fixed' contact-.M1-- Thus, while' the thef'closed position the interiors of vall the` enclos res M are at the same pressure as that wit' in the reservoir O which 'pressure also obv'fithin' the passage F4 by reason of thel bleed passages M8.. By reason. ofthe co-o-perating duid-tight seating surfaces, pressure ilu-idV cannot leak pas-t the contacts. When the valve F3 is opened-the pressurebehind the diaphragm L is relieved so that the predomina-ting pressure within the enclosures M liits thediaphragms L1 awe-.y

from the seating iianges M7 and a blast of deionising duid flows inwards" iii-st over the seatings' Li, M'an'd through thev nozzles `of the fixed contacts M1 to the exhaust passages MS,

ln Figure 7, the-'stack of insulating enclosures N is" mounted on a hollow shedded post insulator P having an internal blast pipe P1V leading upwards from a reservoir Fiin a base F5 upon which the post insulator' P is mounted. The

blast pipe P1 is provided 'with an inlet control :1'

valve P2 operated by "a control piston P3, itself controlled by a trip valve P5, in the base F6. An air break isolating switch Q, whose actuating spindle Q1 lies within a controllchanrber N1 in terposed between the stack of enclosures N and the top of the post insulator P, is operated through a spiral Ygear P6 by a piston P7 controlled, for opening the switch Q, by the piston P3 and, -or closing of the said switch, by a closing valve P3. As'described with reference to Figure 6, each moving contact R1 is carried by a resilient rubber diaphragm R which forms a fluid-tight seating in .co-'operation with a flange S1 on a fixed hollow contacts.

When the circuit-breaker is in the closed condition, the inlet control valve P2 in the blast pipe VP1 is closed and the series break isolating switch Q is also in the closed position. Ii now, the circuit-breaker is to be opened, the trip valve PET is opened so that the piston P3 is lowered and the valve P2 thus opened so that the pressure fluid within the stack of enclosures N lifts the diaphragm R and 'moving contacts R1 thereby causing a blast of deionising iluid to now first over the separated seatings R, S1 and thence through the nozzle-like fixed contacts S to the exhaust conduits s2. The arcs having thus been extinguished the piston P3 permits pressure gas to flow into the cylinder above the piston P'I which movesY down and acts through a rotary vertical operating shaft l?4 and a worm and rack` P9 within the chamber N1 on the spindle Q1 s0 that the switch Q is opened. The inlet control valve P2 is now closed so that the circuitbreaker contacts R1, S automatically reclose under the action of the biasing springs. The circuit-breaker is now ready for reclosingV of vthe circuit by means of the valve P8 controlling the isolating switch Q.

It will be understood that the constructionsv above describeda're given byA way of example: only and that Vdetails. may be modified to "suit requirements. For example, though the deionising uid'. has been described as' compressed air, any other suitable gas, or a liquid, may be employed. .Moreoveig the above examples are described as of the vertical type for convenience ofv description only, and it will be apparent that the Contact enclosure, or stack of enclosures.. may be employed in any position other than the vertical.

The inventionnot only obviates the necessity for providing frictional sliding' or .guide surfaces for thev contacts, which surfaces are vulnerable to; thev eiects of' arcing, but ensures that the moving contact of the circuit-breaker cannot be operated to initiate the arc unless and until the iiliidgp-ressureY necessary to provide the requisite uid" blast at the break is available a-t the. contacts, this advantage being provided whether the enclosure or stack of enclosures is or are main-- tained runder fluid lpressure with control by an outlet control valve, or whether the operation of the contacts is by means of an inlet controlv valve which controls the admission of pressureV prising a :contact enclosure, means whereby iluid under pressure is supplied to the contact enclosure, a rigidly fixed nozzle-like contact within the enclosure and having an exhaust conduit therein, a movable `contact within the enclosure and' 'cooperating with the fixed contact said movable contact being operated by the uid. pressure within the enclosure, and a flexiblel diaphragm within the enclosure locating the movable contact relatively to the iixed Contact so that the movable contact bears resilientl'y against the fixed contact.

2. A fluid-blast electric circuit-breaker as claimed in claim 1, having an auxiliary electrode arranged'within the hollow fixed contact.

3. A circuit-breaker unit for a multi-break fluid-'blast circuit-breaker having a plurality of circuit-breaker units arranged in an aligned assembly or stack, comprising a contact enclosure means whereby fluid under` pressure is supplied 'to the enclosure, two cooperating contacts arranged within said enclosure, at least one of said contacts being movable, 'a resilient device supporting said movable contact and constituting the sole guiding means therefor, and means forl electrically connecting each of said contacts tothe adjacent contact of the next circuit' breaker unit oi' the aligned assembly or stack.

4. A ycontact unit for a multi-break fluidbla'st circuit-breaker having a plurality of contact'un'its' arranged in a series assembly or stack, comprising a contactenclosuremeans whereby fluid under pressure is 4supplied vto the enclosure, a movable contact Aoperated by the fluid pres sure within the enclosure and'ar'ranged' within and towards 'one end'ofy the enclosure, a ilexible mounting device within Vthe enclosure and iconstituting the 'sole guiding means for said mov able Contact within the enclosure, a xed contactv arranged within and towards the other end of the enclosure, and means electrically 'inter-L- connecting the said fixed and' movable contacts whichk respectively cooperate with the corresponding movable and xed contacts of the adjacent units in the stack.

5. A contacty unit as claimed in 'claim 4, in`

which the fixed contact is nozzle-like and communicates with an exhaust passage for the uidblast which flows between the contacts when they separate.

6. A contact unit as claimed in claim 4, in which the ilexible mounting device is of insulating material and the contacts of the unit are electrically interconnected through at least one flexible lead.

7. A multi-break fluid-blast electric circuitbrealrer having a plurality of contact units arranged in an aligned assembly or stack to give a plurality of breaks in series, comprising a plurality or" contact units arranged end to end and in open mutual communication, each unit including a Contact enclosure means whereby uid under pressure is supplied to the enclosure, a movable contact operated by the fluid pressure within the enclosure and arranged within and towards one end of the enclosure, a flexible mounting device within the enclosure and which constitutes the sole guiding means for said movable contact within the enclosure, a iixed contactl arranged within and towards the other end of the enclosure, and means electrically interconnecting the said i'lxed and movable contacts which respectively cooperate with the corresponding movable and xed contacts of the adjacent units in the stack.

8. A multi-break fluid-blast electric circuitbreaker having a plurality of contact units arranged in an aligned assembly or stack to give a plurality of breaks in series, comprising a plurality of contact units arranged end to end in open mutual communication, each unit including a Contact enclosure, a movable contact arranged within and towards one end of the enclosure, a flexible mounting device within the enclosure and which constitutes the sole guiding means for said movable contact within the enclosure, a xed ContactI arranged within and towards the other end of the enclosure, two seating surfaces carried respectively by the two contacts, which seating surfaces respectively cooperate as fluid-tight valve seatings with the corresponding seating surfaces on the contacts of the adjacent units of the stack, and means electrically interconnecting the said xed and movable contacts which respectively cooperate with the corresponding movable and fixed contacts of the adjacent units in the stack.

9. A multi-break fluid-blast electric circuitbreaker as claimed in claim 8, in which the exible locating device for the movable contact of each unit is formed of rubber and constitutes one of the valve seating surfaces.

10. A fluid-blast circuit-breaker as claimed in claim 8, in which the flexible mounting device is formed of rubber and constitutes one of the fluidtight valve seatings.

11. A duid-blast electric circuit-breaker comprising a contact enclosure, means whereby fluid under pressure is supplied to the said enclosure, a rigidly fixed contact within the enclosure, a movable contact within the enclosure and cooperating therein with the fixed contact, at least one of said contacts having a gas-discharge vent therein, whilst the movable contact is operated solely by the fluid pressure within the enclosure, and a resilient device within the enclosure and supporting the movable contact therein, the movement of the movable contact being guided solely by said resilient device, so that frictional sliding or guide surfaces for the moving contact, as well as operating mechanism therefor, are obviated.

12A fluid-blast electric circuit-breaker comprising a contact enclosure, means whereby fluid under pressure is supplied to the enclosure, a rigidly fixed contact within the enclosure, a movable contact within the enclosure and cooperating therein with the iixed contact, at least one of said contacts having a gas-discharge vent therein whilst the moving contact is operated solely by the fluid pressure within the enclosure, and a exble metal diaphragm within the enclosure and supporting the movable contact therein, the movement of the movable contact being guided solely by said diaphragm, so that frictional sliding or guide surfaces for the moving contact, as well as operating mechanism therefor, are obviated.

13. A fluid-blast electric circuit-breaker comprising a contact enclosure, means whereby fluid under pressure is supplied to the enclosure, a rigidly xed contact within the enclosure, a movable contact within the enclosure and cooperating therein with the xed contact, at least one of said `contacts having a gas-discharge vent therein whilst the moving contact is operated solely by the fluid pressure within the enclosure, and a flexible rubber diaphragm within the enclosure and supporting the movable contact therein, the movement of the movable contact being guided solely by said diaphragm, so that frictional sliding or guide surfaces for the moving contact, as well as operating mechanism therefor, are obviated.

14. A fluid-blast electric circuit-breaker comprising a contact enclosure, means whereby iluid under pressure is supplied to the enclosure, and a rigidly fixed contact within the enclosure, a movable Contact within the enclosure and cooperating therein with the fixed contact, at least one of said contacts having a gas-discharge vent therein, means whereby the movable Contact is operated solely by the fluid pressure Within the enclosure, a resilient device within the enclosure and supporting the movable contact therein, the movement of the movable contact being guided solely by said resilient device so that frictional sliding or guide surfaces for the moving contact, as well as operating mechanism therefor, are obviated, and seatings carried by the two contacts respectively, the said seatings constituting relatively movable parts of a fluid-tight valve which controls the flow of arc quenching duid from the enclosure to the said discharge vent.

DONALD FOSTER AMER.

REFERENCES CITED The following references are of record in the le of this patent:

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